Vegetable leaf top dressing must pay attention to the following points

1. Spray concentration should be appropriate. Foliar top dressing must control the spray concentration. If the concentration is too high, it is easy to cause fat damage and cause unnecessary loss. Especially for trace element fertilizers, the critical range between vegetables from lack to excess is narrow and more strictly controlled. If the concentration is too low, it will not receive the desired effect. 2. Spray time should be appropriate. One of the main factors affecting the effect of foliar topdressing is the wet time of the fertilizer on the leaf surface. The longer the wetting time, the more nutrients are absorbed by the leaf surface, and the better the effect. Therefore, foliar topdressing must choose the appropriate spraying time according to the weather conditions. Generally, it is best to use early, late or cloudy days on sunny days. Foliar topdressing can not be carried out before rain or rain. If it rains within 3 hours after spraying, it should be sprayed once after sunny days, but the spraying concentration should be reduced appropriately. 3. Fertilizer should be used properly. When foliar topdressing, two or more foliar fertilizers can be reasonably mixed, and the yield increase effect will be more significant, and the spraying time and labor can be saved. However, after the fertilizer is mixed, there must be no adverse reactions or no reduction in fertilizer efficiency, otherwise the purpose of mixing may not be achieved. In addition, the concentration of the solution and the pH should be paid attention to when the fertilizer is mixed; in general, the pH value of the solution is 6 to 7 to facilitate the absorption of the leaves. 4. The quality of the spray should be guaranteed. Foliar top dressing requires fine droplets and even spray, especially pay attention to spraying the upper leaves and the back of the leaves. Because the new leaves are faster than the old leaves and the back of the leaves than the positive ones, the absorption capacity is strong.

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